Embodiments of the present invention relate to the generation of a laser beam pattern on a substrate.
A laser beam pattern generator modulates and scans a laser beam onto a substrate to generate a pattern on the substrate. The laser beam is modulated in accordance with the pattern to be generated on the substrate. For example, a typical pattern generator comprises a substrate support to hold the substrate, and laser beam source, focusing, modulating, and scanning components, to generate, modulate, and scan a laser beam across the substrate to form a laser beam pattern on the substrate. The substrate support comprises a support motor to move the substrate support in coordination with the beam scanning component. Typically, the scanning component is a rotating scanner comprising a plurality of mirror facets. The substrate may be, for example, a mask blank used to fabricate semiconductors, that is exposed to the modulated laser beam to write a circuit image onto photosensitive material of the mask blank. The mask blank is then developed and stabilized to form a mask for the fabrication of integrated circuits.
It is desirable to be able to use the mask to generate high resolution laser beam patterns, with good accuracy, on a substrate. However, in practice the resolution of the laser beam generated pattern is often degraded by substrate positioning defects occurring in the laser beam pattern generator. For example, the support motor may not accurately or reproducibly move the substrate support so that the resultant position of the substrate is not its desired location. In conventional laser beam pattern generator systems, the erroneous stage and substrate position may be determined, by for example, methods such as interferometry. The position of the laser beam is then adjusted by deflecting the laser beam a suitable amount to compensate for the improper substrate position, by for example, deflecting a steering mirror system, as for example, described in
U.S. Pat. No. 4,796,038 to Allen et al, entitled xe2x80x9cLaser Pattern Generation Apparatus,xe2x80x9d which is incorporated herein by reference in its entirety. While such correction methods improve the resolution and accuracy of the laser beam pattern generation, the resolution is still not as fine as that desirable, and the accuracy is also not as good as needed. Thus, it is desirable to have a laser beam pattern generator and method to generate higher resolution and more accurate laser beam scanning patterns.
A laser beam pattern generator comprising:
a substrate support capable of supporting a substrate, the substrate support comprising a support motor;
a laser beam source to generate a laser beam;
a beam modulator to modulate the intensity of the laser beam according to a pattern;
a rotating scanner comprising a plurality of mirror facets capable of rotating at a spinning frequency to scan the laser beam across the substrate;
a rotating scanner compensator to deflect the laser beam according to a rotating scanner correction signal comprising a harmonic of the spinning frequency to compensate for errors in the scanning of the laser beam arising from the rotating scanner; and
a controller comprising program code to control the substrate support, laser beam source, beam modulator, rotating scanner, and rotating scanner compensator, to modulate and scan the laser beam across the substrate to generate the pattern on the substrate,
whereby a corrected laser beam pattern is generated on the substrate.
A laser beam pattern generator comprising:
a substrate support capable of supporting a substrate, the substrate support comprising a support motor;
a laser beam source to generate a laser beam;
a beam modulator to modulate the intensity of the laser beam according to a pattern;
a rotating scanner comprising a plurality of mirror facets capable of rotating at a spinning frequency to scan the laser beam across the substrate;
a rotating scanner compensator to deflect the laser beam according to a rotating scanner correction signal to compensate for errors in the scanning of the laser beam arising from the rotating scanner; and
a controller comprising program code to control the substrate support, laser beam source, beam modulator, rotating scanner, and rotating scanner compensator to modulate and scan the laser beam across the substrate to generate the pattern on the substrate, the controller adapted to generate the rotating scanner correction signal of the form xcexa3An Sin(nxcfx89t+xcfx86n), where An is a coefficient, t is time, n is the order of the harmonic, xcfx89 is the spinning frequency, and xcfx86n is a phase shift, to compensate for errors in the scanning of the laser beam arising from the rotating scanner, and pass the signal to the rotating scanner compensator,
whereby a corrected laser beam pattern is generated on the substrate.
A method of generating a pattern on a substrate comprises placing a substrate on a substrate support, generating a laser beam, modulating the intensity of the laser beam according to a pattern, rotating a beam scanner at a spinning frequency to scan the laser beam across the substrate, and deflecting the laser beam according to a rotating scanner correction signal that comprises a harmonic of the spinning frequency to compensate for errors in the scanning of the laser beam arising from the rotating scanner, thereby generating the pattern on the substrate.